Liquid crystal displays use an electrical field to display the images by adjusting the light transmittance of the liquid crystals. That is, the liquid crystal displays use the electrical field which is formed between a picture electrode and a common electrode, which face an upper and lower substrates, and drive the liquid crystals.
Liquid crystal displays include a thin film transistor array substrate (being the lower substrate), a color filter array base (being the upper substrate), spacers (hereinafter, referred to as spacer particles) which retain cell gaps between the above substrates, and liquid crystals which fill the cell gap.
The thin film transistor array substrate is structured of a large number of signal wiring lines and thin film transistors, and an alignment layer which is placed on the above members for the liquid crystal orientation. The color filter array substrate is structured of a color filter for color reproduction, a black matrix to prevent light leakage, and the alignment layer coated onto the above for liquid crystal orientation.
Conventionally, the above described spacer particles were sprayed onto the substrate by a spacer particles spraying device, which was known as a spray method.
However, by such spray method, the spacer particles tended to be spread unevenly. Specifically, if any aggregation of the spacer in the displayed element is distinctly observed, it deteriorates the quality level of the liquid crystal display, which is of course a major problem. Further, in the case that a substrate incorporating an active element, such as TFT, if any spacer exists on a projected TFT, and if force is applied to the substrate, the TFT tends to be damaged, which was also a major problem.
Due to this, it is desired that a section is designated for placement of the spacer particles to keep them away from TFT, or the spacer particles are placed on a light shielding film. To resolve this, it is proposed that the spacer particles are arranged by a printing method, or that the spacer particles are arranged at specified locations by a special dispenser or an inkjet apparatus.
Among these methods, the inkjet apparatus can arrange spacer particles one by one at accurate locations, and an inkjet head having plural nozzles can arrange a large number of these spacer particles at the specific locations at the same time, which results in high productivity.
However, in this inkjet apparatus for ejecting the above spacer particles, a solvent, including large sized spacer particles whose diameter is several μm for example, is ejected for arranging the spacer particles, and which absolutely differs from the normal use of the inkjet apparatus which ejects colored liquid ink. Due to this, it is very essential that the spacer particles are evenly mixed in the jetting liquid supplied to the inkjet heads. Further, it is also essential that the spacer particles exist uniformly in the ejection head.
If the spacer particles exist unevenly in the ejecting liquid, ejection tends to become unstable or to malfunction, further the number of the spacer particles in the ejecting liquid changes due to the change of density, which result in major problems of the ejection characteristics. Accordingly, in a tank which supplies the ejecting liquid, being the solvent including the spacer particles, a mixing operation is necessary to uniformly disperse the spacer particles in the solvent.
For this purpose, an apparatus is known which simultaneously supplies the liquid crystals and the spacer particles. In this apparatus, a mixing device, having a motor driven screw, is provided in the tank in which the spacer particles are evenly dispersed in the liquid crystals (see Patent Document 1).
Further, a method is disclosed in which a pressuring chamber is vibrated by a piezo element to evenly disperse the spacer particles (see Patent Document 2).
[Patent Document 1] Unexamined Japanese Patent Application Publication No. 5-281,562
[Patent Document 2] Unexamined Japanese Patent Application Publication No. 2000-66,215